Subject: will history repeat itself?

From: Steve Allen <[email-masked]>
Date: Sat, 10 May 2003 03:14:45 -0700

The existence of the ITU-R working group to study UTC strongly
resembles the situation 33 years ago when leap seconds were first
being proposed.  At that time CCIR working group VII-1 was studying
how radio broadcast time signals could provide standard time interval
and frequency (both using atomic seconds) and also provide time-of-day.

The complete history is probably not available even by reading the
transactions of all of the international scientific and treaty
organizations.  The IAU proceedings and transactions from
1970 and 1973 shed some light on what happened.

In 1968 the CCIR (predecessor to the ITU-R) formed the working group.
Then, as now, the membership of the working group overlapped
significantly with the membership of the commissions of several
international scientific and treaty organizations.

The 1970 report of IAU Commission 31 (Time) indicates that in autumn
of 1969 there was a proposal that indicated "the urgent need that a
Consultative Committee for Time Scales be created by the CIPM, being
charged with the preparation of the time scale definition work and
giving outlines to a laboratory working under these auspices, at best
the BIH".  The proposal was supported at meetings of URSI, CCIR, and
CIPM, was recommended in a resolution of URSI, and explicitly stated
"that the definition of astronomical time scales does pertain to the
IAU".  But in October 1969 the CCIR working party rediscussed the
question, and submitted their documents to the January 1970 Plenary
Assembly of the CCIR for a final decision.  They did ask the opinion
of the Scientific Unions concerned.

The results of this activity show up in the 1970 proceedings of
IAU commissions 31 and 4 (Ephemerides), who held joint meetings
to discuss some aspects.  The publications of the IAU are normally
quite restrained, but in this instance there are indications that
the meetings were sufficiently disturbed that some issues did not
get resolved until the 1973 IAU General Assembly.

The recommendations from the CCIR were effectively the system of UTC
with leap seconds that we have now, and it was reported that the CCIR
resolved that the IAU should be informed of them.  Not all of the
astronomers were happy with the system, but they were even less happy
that the IAU had never received official communication from the CCIR
about those recommendations.

In the end commission 31 adopted a resolution consisting of
supplementary recommendations about the new form of UTC, and noted
that they considered the scheme to be the optimum solution in the
presence of the conflicting requirements of UTC users.

In 1973 IAU commissions 31 and 4 held a joint session which produced
two resolutions regarding UTC.  The first recognized that UTC
"provides mean solar time directly to a precision that is needed for
navigation and surveying" and recommended that UTC be the basis for
standard time.  The second refined the rules regarding when leap
seconds might be inserted into UTC (and these rules were adopted).
They also made several recommendations, the last one of which
might relate to the incidents in 1970:

    Close cooperation between the scientific and treaty organizations,
    CIPM, CCIR, IUGG, URSI and IAU, must assure that the present
    evolution in worldwide standardization in the provision and use of
    precise time can continue in an orderly way.

It will be interesting to see whether this recommendation produces
more civil contents in the proceedings for the next few trienniums of
the international scientific unions.

--
Steve Allen          UCO/Lick Observatory       Santa Cruz, CA 95064
[email-masked]      Voice: +1 831 459 3046     http://www.ucolick.org/~sla
PGP: 1024/E46978C5   F6 78 D1 10 62 94 8F 2E    49 89 0E FE 26 B4 14 93